US4381229A - Process for electrochemical reduction of terephthalic acid - Google Patents
Process for electrochemical reduction of terephthalic acid Download PDFInfo
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- US4381229A US4381229A US06/319,120 US31912081A US4381229A US 4381229 A US4381229 A US 4381229A US 31912081 A US31912081 A US 31912081A US 4381229 A US4381229 A US 4381229A
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- terephthalic acid
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/25—Reduction
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
- C07C51/367—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by introduction of functional groups containing oxygen only in singly bound form
Definitions
- This invention relates to a process for the electrochemical reduction of terephthalic acid to p-hydroxymethylbenzoic acid (pHMBA) and more particularly to improvements in the electrical efficiency of the said reaction and to operation by treatment of the cathode to obtain a mercury overlay as an amalgam on the cathode surface and the addition of a soluble salt of mercury, which regenerates the amalgam overlay, to the electrolysis catholyte solvent.
- pHMBA p-hydroxymethylbenzoic acid
- an object of the present invention to develop an electrochemical process for the manufacture of p-hydroxymethylbenzoic acid from terephthalic acid which avoids the above disadvantages. It is an object of the present invention to provide a process for production of p-hydroxymethylbenzoic acid wherein the production of by-product impurities, namely, 4-carboxybenzaldehyde, dihydroxymethylbenzene and toluic acid is minimized. It is a further object of this invention to increase the current efficiency of the electrochemical reduction process over that of previously known methods for electrochemical reduction of terephthalic acid to p-hydroxymethylbenzoic acid.
- Terephthalic acid is electrochemically reduced to p-hydroxymethylbenzoic acid in a process in an electrolysis cell in which (a) the cathode is solid and metal with a mercury overlay as an amalgam surface and has a hydrogen overvoltage which is greater than the potential for the reduction of terephthalic acid to p-hydroxymethylbenzoic acid, and (b) sufficient mercury is added as a mercury compound to maintain the process. Addition of a mercury compound is essential. For example, current efficiency decreases in continuous operation and cathode amalgam surfaces lose amalgamation without addition of a mercury compound.
- current efficiency is defined as ratio of consumption in Faradays used to make product to total Faradays used times 100.
- amalgam is defined as referring only to an alloy of mercury.
- the present invention provides a process for the electrochemical preparation of p-hydroxymethylbenzoic acid with improved current efficiency and minimal production of by-product impurities.
- the process comprises performing the cathodic reduction in an electrolysis cell having a cathode compartment and an anode compartment.
- the anode and cathode compartments can be separated by a cation exchange diaphragm, although the presence of a separating diaphragm is not an essential element of the invention. If a separating diaphragm is used, the cathode and anode and the separating diaphragm are preferably in parallel planes.
- several of the elementary electrolysis cells can be combined in the manner of a filter press.
- any metal with a higher hydrogen overvoltage than the potential for the reduction of terephthalic acid to p-hydroxymethylbenzoic acid which will form an alloy with lead and an amalgam with mercury is suitable.
- material forming the cathode are lead and alloys of lead with cadmium, antimony, tin or bismuth.
- the cathode is prepared by abraiding in a suitable manner the surface of the solid cathode to remove any metal oxidation and then contacting the abraided metallic surface with mercury to form the amalgam.
- Liquid mercury of 99.9% purity is used as a bath for the abraided solid lead cathode.
- the lead amalgam is formed in the surface of the lead at room temperature upon contacting the mercury bath.
- the anode of the electrolysis cell usually consists of a solid electrically conducting material which is electrochemically stable in the anolyte and under the operating conditions considered.
- a solid electrically conducting material which is electrochemically stable in the anolyte and under the operating conditions considered.
- metals and metalloids such as platinum, platinised titanium, graphite, lead and its alloys, particularly with silver, antimony or tin.
- any known cation exchange membrane can be used to separate the catholyte from the anolyte, but membranes of the homogeneous type are preferred. These membranes optionally can be reinforced with a screen. For carrying out electrolysis operations over a long period, it is naturally preferred to use membranes which do not swell and which are stable to the action of the various constituents of the catholyte and the anolyte. Examples of such membranes are those of Nafion (trademark of E. I. DuPont de Nemours & Co.) perfluorosulfonic acid.
- the catholyte can comprise a neutral solvent, a weakly basic solvent or an aprotic solvent i.e., acetonitrile, to which a source of protons has been added.
- neutral solvents are water, methanol and other alcohols mixed with water to obtain necessary solvent properties.
- basic solvents are ammonia, methylamine, ethylenediamine which are diluted suitably to maintain a weak basic condition.
- the catholyte consists of a solvent, preferably water, and terephthalic acid with a soluble ammonium salt and ammonia. At the start of electrolysis, the catholyte contains sufficient ammonia to form a diammonium salt of terephthalic acid.
- Concentration of ammonia as ammonium hydroxide is within the range of from about 1 gram of ammonium hydroxide per 2 grams of terephthalic acid to about 1 gram of ammonium hydroxide per gram of terephthalic acid and wherein the pH of the resulting solution is at least 6.5, preferably with a pH within the range of from about 8.5 to about 9.5.
- concentrations of terephthalic acid and ammonium salt can be either constant when the reaction is carried out continuously, or variable when the reaction is carried out discontinuously.
- the concentration of terephthalic acid is less than the saturation concentration at the temperature of electrolysis; generally, this concentration is greater than 2% by weight, and preferably greater than 3% when the current density is high, these values relating particularly to the constant concentration when the reaction is carried out continuously and to the final concentration when the reaction is carried out discontinuously.
- the concentration of ammonium salt is usually between about 0.1% to about 10% by weight, and preferably between about 0.1% to about 1.0% by weight, these values relating particularly to the total solution of water, terephthalic acid and other solution components when the reaction is carried out continuously and to the final solution when the reaction is carried out discontinuously.
- the ammonium salt can be any ammonium salt but a salt selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium carbonate is preferred.
- the catholyte can also contain reaction by-products in small amounts, generally less than 1% by weight.
- An aqueous acid solution is preferably used as the anolyte, though any other anolyte capable of providing electrical conductivity between the two electrodes can be used.
- Aqueous solutions of sulphuric or phosphoric acids are usually employed in a concentration generally of 0.1 to 5 mols/liter, and preferably 0.5 to 2 mols/liter.
- the current density at the cathode is within the range of from about 1 to about 200 amperes per decimeter squared (A/dm 2 ), preferably from about 20 to about 100 A/dm 2 .
- the flow of the catholyte in a closed circuit is usually achieved by means of a pump.
- the circuit can in addition contain attached devices such as a heat exchanger or an expansion vessel.
- the expansion vessel enables terephthalic acid to be added to the catholyte and also some catholyte to be withdrawn in order to extract the p-hydroxymethylbenzoic acid. By-product hydrogen is also removed.
- the anolyte can also be circulated, preferably in an anolyte circuit similar to that of the catholyte, so that the pressure on either side of the separating diaphragm can be substantially the same.
- At least one spacer is preferably present in the anode and cathode compartment if a cation exchange membrane is used. These spacers serve to prevent deformations of the cation exchange membrane and prevent contact between this membrane and the electrodes. These spacers also help to render uniform the spacing between the membrane and electrodes which contains the electrolyte.
- These spacers are generally manufactured from synthetic polymers which are chemically inert and which do not conduct electricity; they can be made in the form of interlaced, intertwined, knotted or welded yarns (e.g., woven fabrics, grids or nets) or they can be in the form of plates possessing holes or grooves. In practice, these spacers are oriented along planes which are parallel to those of the electrodes and the separating diaphragm.
- Terephthalic acid reduction can be monitored to obtain 100% conversion. Less than 100% conversion is preferable. Less than 96% conversion is more preferable. Undesirable by-products are produced at high conversion levels. Increased amounts of impurities such as dihydroxymethylbenzene and toluic acid can result at terephthalic acid conversion levels of greater than 95-96%. Percent conversion is preferably balanced to obtain maximum conversion to p-hydroxymethylbenzoic acid and minimum conversion to undesirable by-products.
- Terephthalic acid under ambient conditions being virtually insoluble in water, requires a weak base as a reactant to form a soluble salt in water.
- suitable weak bases are ammonia, methylamine and ethylenediamine but any similar weak base can be used.
- a weak base such as ammonia and a salt such as an ammonium salt are added initially to the catholyte, the ammonia in a concentration sufficient to dissolve the terephthalate acid in the solvent, i.e., water, liquid ammonia, etc. but which is preferably water, and a ammonium salt to carry the current.
- a monoammonium salt of terephthalic acid is added to maintain a basic condition sufficient to cause additions of terephthalic acid to dissolve, with pH above 6.5 and preferably with a pH within the range of about 8.5 to about 9.5, to insure complete solubility of the terephthalic acid.
- a mercury compound preferably a solvent-soluble mercury salt
- a mercury compound is added to the catholyte in an amount sufficient to maintain the continuous process, to provide a minimum concentration of mercury metal ion of from about 5 to 1000 parts per million (ppm) expressed as the metal. Concentrations of mercury metal ions greater than 1000 ppm can be used if suitable. Examples of mercury salts soluble in aqueous solutions are mercuric acetate, mercuric bromide, mercuric chlorate, mercuric chloride, mercuric cyanide. Mercuric acetate is preferred because of high solubility and easy availability.
- the p-hydroxymethylbenzoic acid is isolated from the electrolyte by known means, which optionally can be by the difference in water solubility between that of terephthalic acid and p-hydroxymethylbenzoic acid.
- the catholyte is acidified and filtered hot, within a temperature range of from about 75° C. to about 100° C., to remove terephthalic acid.
- the p-hydroxymethylbenzoic acid is obtained by cooling the mother liquor, optionally after concentrating under reduced pressure. The cooling is carried out at temperatures below 40° C. and preferably below 25° C., the degree of concentration and the cooling temperature naturally vary according to the degree of purity desired for the p-hydroxymethylbenzoic acid.
- the process of the invention possesses numerous advantages in addition to the advantages of continuous operation; it makes it possible to use catholyte solutions which facilitate workup and recovery of the p-hydroxymethylbenzoic acid; it allows electrolysis cells to be produced which are compact and easy to dismantle; it allows gases to be removed easily which are produced at the anode, especially oxygen, and are capable of causing high resistance between the electrodes due to gas bubbles; it makes it possible to use high current densities and to achieve easily the supply of electricity in series between the various elementary electrolysis cells in an assembly of several cells; it makes it possible to use cells with vertical electrodes.
- the anolyte and the catholyte can be circulated very rapidly, enabling lower concentrations of terephthalic acid to be employed and, as a result, better degrees of conversion can be obtained in continuous operation.
- Batch reduction of terephthalic acid to p-hydroxymethylbenzoic acid was carried out in an electrolysis cell in the following manner.
- the cell was mounted in an oil bath which was used to heat the electrolyte to reaction temperature before starting and to cool the electrolyte once the reaction had started.
- the oil bath was fitted with an electric heater, a source of cooling comprising coils filled with cooling water and a mechanical stirring means.
- the cell was a 600 ml glass beaker fitted with a stopper of fluorocarbon rubber. Holes through the stopper gave entrance to a thermometer, the anode leads and the cathode leads.
- the anode support was a glass anolyte tube which was fitted with a fluorocarbon plastic holder to support the anode and a semi-permeable membrane.
- the anode was a circular platinum screen about 2.5 cm in diameter.
- the membrane was of sulfonated fluorocarbon polymer.
- the glass tube served as the anolyte chamber.
- the fluorocarbon plastic holder was inclined at an angle from the horizontal to permit gases rising from the cathode to escape.
- the cathode was a metal disc about 6 cm in diameter.
- the cathode was of electrolytically pure lead of 99.9% purity.
- a magnetic stirring bar was placed on top of the cathode disc in the bottom of the glass beaker which served as the electrolysis cell.
- the catholyte solution was placed in the cell with the cathode and with the stirring bar in place.
- the anode was inserted in the anolyte chamber, the chamber was filled with anolyte and inserted in the fluorocarbon stopper.
- the anolyte chamber was thereupon checked for membrane leakage and placed on the cell.
- the thermometers were inserted in the fluorocarbon stopper and the cell was assembled.
- Heat can be applied to the completed cell by means of an oil bath to reach the necessary temperature at which time the heat application is stopped.
- the cooling system is thereupon activated and as soon as the cell temperature began to drop, the electrolysis reaction is started by applying a source of direct current. Alternatively, the reaction could be started at room temperature and reach operating temperature without direct heating. Alternatively, the cell could be operated without the presence of a semipermeable membrane.
- Runs No. (5302) 24.sup.(a) and 28.sup.(a) duplicate run conditions of Comparative Run (c) based on calculated current efficiency, except that the runs were not interrupted and the cells were not shorted. It is presumed that application of 15.3 Faradays per mole of terephthalic acid in Runs No. (5302) 24.sup.(a) and 28.sup.(a) would have resulted in 100% terephthalic acid conversion. Run (5302) 26.sup.(b) using interrupted operation resulted in lower conversion of terephthalic acid than Runs No. (5302) 24 and 28, indicating that interrupted operation did not improve current efficiency under these conditions.
- Example II The procedure of Example I was repeated using ammonium chloride and ammonium sulfate as the ammonium salts. The results are in Table II.
- ammonium chloride is a more suitable electrolyte salt with a lead cathode than either ammonium carbonate or ammonium sulfate.
- the chloride ion is at least twice as effective as the carbonate or sulfate ions.
- Example II The procedure of Example I was repeated using ammonium chloride and ammonium sulfate as the ammonium salts and mercury as the cathode.
- the liquid mercury was placed in the bottom of the glass beaker which functioned as the cell holder. Electrical contact was made with the liquid mercury by means of a suitable conductor. Results are in Table III.
- Example II The procedure of Example I was repeated using a lead amalgam cathode.
- the lead amalgam was prepared by abraiding the surface of electrolytically pure lead to remove any metal oxidation and then contacting the abraided metal surface with mercury to form the amalgam.
- Mercury of 99.9% purity was used as the bath for the abraided solid lead cathode.
- the lead amalgam of mercury formed in the surface of the lead at room temperature. Results are in Table IV.
- Two continuous reductions of terephthalic acid to p-hydroxymethylbenzoic acid were carried out in an electrolysis cell in the following manner to compare the current efficiency obtained with a lead cathode and with a lead amalgam cathode in continuous operation.
- One cathode was electrically pure lead.
- the other cathode was electrically pure lead amalgamated with 99.9% pure mercury.
- the two compartment electrolysis cell comprised an inlet plate of polyvinylchloride (PVC) which was fitted to a second plate of the same size of lead amalgam which constituted the cathode.
- PVC inserts between the cathode plate and the semipermeable membrane acted as spacers to separate the cathode and membrane sufficiently to permit catholyte flow.
- the anode was an electrically pure 1/2-inch titanium plate coated with platinum to a thickness of 250 micro-inches. Anode and membrane were separated by PVC spacers to permit the anolyte to flow through the cell. An external reservoir for the anolyte served as an oxygen gas separator. An external reservoir for the catholyte served as a hydrogen gas separator. In operation, electrolyte was continuously pumped from the reservoir to the electrolysis cell and returned to the reservoir through a heat exchanger. No addition of a mercury salt was made to either catholyte. Details are in Table V.
- Ammonium chloride (NH 4 Cl) was used as the electrolyte with the lead cathode on the basis of data in Example II indicating NH 4 Cl gave higher terephthalic acid (TA) conversion to pHMBA and higher current efficiency than did ammonium sulfate (NH 4 ) 2 SO 4 as an electrolyte.
- TA terephthalic acid
- Example V The lead amalgam cathode used in Examples V and VI was re-amalgamated in the procedure of Example IV.
- the procedure of Example V was repeated without any addition of mercury.
- the electrolyte was analyzed three times by atomic absorption (AA) of mercury using standard analytical techniques, twice before the 5-hour run and once after the 5-hour run.
- the first analysis was of the freshly prepared catholyte.
- the second analysis was after pumping the catholyte through the cell so as to contact the lead amalgam cathode.
- Mercury content of the catholyte was increased by contact with the lead amalgam cathode and, as indicated by the third analysis, decreased with subsequent reduction of terephthalic acid. Details are in Table VII.
- Example V In the procedure of Example V two continuous reductions of terephthalic acid were carried out in an electrolysis cell to compare current efficiency obtained with and without the addition of a mercury salt.
- the cathode was electrically pure lead amalgamated with 99.9% mercury.
- Periodic additions of mercuric acetate (Hg(Ac) 2 ) were made each hour to the electrolysis cell during the course of the run.
- a control run was also made wherein mercuric acetate was not added to the electrolysis cell.
- the results of continuous operation using ammonium sulfate as the required salt are in Table VIII.
- Example V The procedure of Example V was repeated in multiple runs using mercuric acetate additions in all runs.
- the same cathode used in Example VIII was used in Example IX without cleaning and/or amalgamation with a mercury bath.
- the results of continuous operation using ammonium sulfate and one run with ammonium carbonate as the required salt and with addition of mercuric acetate over a period of days are in Table IX.
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Abstract
Description
TABLE I ______________________________________ Electrochemical Reduction of Terephthalic Acid - (NH.sub.4).sub.2 CO.sub.3 Electrolyte LEAD CATHODE Compar- ative Run No. (5302) 24.sup.(a) 28.sup.(a) 26.sup.(b) Run.sup.(c) ______________________________________ Conditions (NH.sub.4).sub.2 CO.sub.3 - g/l 15 15 15 13.6 Ammonia - g/l * * * 16 Terephthalic Acid (TA) - g/l 50 50 50 42.3 Current Density - A/dm.sup.2 6.5 6.5 6.5 10 Faradays/mole TA 3.7 3.7 3.7 15.3 Actual Run Time - Minutes 120 120 120 300 Results TA Conversion 36 35 18 100 pHMBA-Yield 25 27 8 91 Current Efficiency 27 29 9 (26).sup.(c) Catholyte Analysis** - End of Run - mg/ml pHMBA 10.2 11.2 3.58 N.R. Terephthalic Acid (TA) 28.2 29.8 37.9 N.R. 4-CBA 0.54 0.18 0.56 N.R. ______________________________________ Notes: N.R. -- Not reported. *Ammonia was added until terephthalic acid dissolved. **Analysis of product by liquid chromatography. .sup.(a) Continuous operation with no interruption. Cells were not shorted. .sup. (b) Interrupted operation 15 minutes on, 1 minute off until 120 minutes. Cell was not shorted out. .sup.(c) Data from Germ. Offen. 2,642,496. Current efficiency (C.E.) is calculated. Cell was shorted out for 1 minute each hour.
TABLE II ______________________________________ Electrochemical Reduction of Terephthalic acid - NH.sub.4 Cl - (NH.sub.4).sub.2 SO.sub.4 Electrolytes Lead Cathode Run No. (5302) 8 20 25 ______________________________________ Conditions NH.sub.4 Cl - g/l 10 10 (NH.sub.4).sub.2 SO.sub.4 - g/l 15 Ammonia - g/l 14 * * Terephthalic Acid (TA) - g/l 50 100 50 Current Density - (C.D.) A/dm.sup.2 6.5 6.5 6.5 Faradays/mole TA 3.7 3.7 3.7 Actual Run Time - Minutes 120 240 120 Results TA Conversion 72 83 51 pHMBA-Yield 60 56 31 C.E. 64 60 32 Catholyte Analysis** - End of Run - pHMBA, mg/ml 26.7 47.4 13.9 Terephthalic Acid (TA), mg/ml 13.9 15.9 24.0 4-CBA, mg/ml 0.29 0.73 0.35 ______________________________________ *Ammonia was added until terephthalic acid dissolved. Measured pH was les basic than Run 8. **Analysis by liquid chromatography.
TABLE III ______________________________________ Electrochemical Reduction of Terephthalic Acid - Mercury Cathode Run No. (5302) 144 162 136 ______________________________________ Conditions Salt NH.sub.4 Cl (NH.sub.4).sub.2 SO.sub.4 NH.sub.4 Cl g/l 20 40 20 Ammonia 26 32 24 g/l Terephthalic Acid (TA) 123 197 117 g/l C.D. - A/dm.sup.2 12 12 12 Faradays/Mole of TA 3.7 3.7 3.7 5.6 Time - Minutes 120 120 120 180 Results - % TA Conversion 97 96 97 98 pHMBA Yield 85 93 89 74 C.E. 91 99 96 53 Catholyte Analysis** - End of Run - mg/ml pHMBA 96.5 167.3 92.8 77.1 Terephthalic Acid (TA) 3.22 8.2 3.32 2.72 4-CBA 0.48 1.2 0.34 0.07 Toluic Acid 0.67 0.9 0.74 6.45 p-Xylenediol N.D. N.D. N.D. 13.6 ______________________________________ Note: N.D. -- Not detected by liquid chromatography. **Analysis by liquid chromatography.
TABLE IV ______________________________________ Electrochemical Reduction of Terephthalic Acid - Lead Amalgam Cathode (5302) (5593) (5593) Run No. 196 100 102 ______________________________________ Conditions Salt (NH.sub.4).sub.2 (NH.sub.4).sub.2 (NH.sub.4).sub.2 SO.sub.4 SO.sub.4 SO.sub.4 g/l 40 40 40 Ammonia - g/l 23 21 30 Terephthalic Acid (TA) g/l 107 106 169 C.D. - A/dm.sup.2 13.5 13.5 13.5 Faradays/Mole of TA 3.7 3.7 3.7 Time - Minutes 120 120 240 Results - % TA Conversion 92 87 88 pHMBA Yield 93 84 83 C.E. 99 91 89 Catholyte Analysis** - End of Run - mg/ml pHMBA 91.7 82.4 128.2 Terephthalic Acid (TA) 8.9 13.5 19.9 4-CBA 1.0 1.9 0.7 Toluic Acid N.D. N.D. N.D. ______________________________________ Note: N.D. -- Not detected by liquid chromatography. **Analysis by liquid chromatography.
TABLE V ______________________________________ Reduction of pHMBA Current Efficiency - Continuous Operation Lead and Lead Amalgam Cathodes Run No. Run No. 5268-164 5593-140 ______________________________________ Conditions Cathode Lead Lead Amalgam Salt NH.sub.4 Cl (NH.sub.4).sub.2 SO.sub.4 g/l 10 30-44 pH 7.0-9.0 8.4-9.1 TA - g/l 20-100 40-120 Current Density A/dm.sup.2 6.5-13 50 Results pHMBA - % Current Efficiency 0-2 Hours of Run 57 86 2-4 Hours of Run 21 71 4-6 Hours of Run 4 41 ______________________________________
TABLE VI ______________________________________ EDAX Analysis of Lead Amalgam Cathode Surfaces Element, % Hg Pb Fe ______________________________________ Freshly Amalgamated 74 26 -- After Run - No Hg Added Top Layer Surface 22 77 0.6 Fresh Surface 32 67 0.3 ______________________________________
TABLE VII ______________________________________ Loss of Mercury From Catholyte During Reduction Run 5995-1 ______________________________________ Conditions Cathode Lead Amalgam Electrolyte (NH.sub.4).sub.2 SO.sub.4, g/l 46 Ammonia, g/l 12 pH - Start/End 8.2/9.0 Current Density, A/dm.sup.2 54 TA, g/l 48-130 Results C.E. % pHMBA - During 5 Hr Run 90 ± 3 H.sub.2 Prod. - ft..sup.3 - Total over 5 Hrs 1.2 Analyses of Catholyte Hg Pb Freshly Prepared Catholyte 10 ppb 0.2 ppm Catholyte After Pumping Through Cell over Cathode for 10 minutes, No current applied 625 ppb 10 ppm Catholyte After 5 Hr Reduction of TA 400 ppb 5 ppm ______________________________________ Note: ppb -- parts per billion. ppm -- parts per million.
TABLE VIII ______________________________________ Reduction of Terephthalic Acid to pHMBA In Presence of Hg In Catholyte Runs 5995 Time - Hrs 13 22.sup.(a) (No Hg Added) (With Addition of Hg) H.sub.2 /1/2 Hr. C.E./ Accum. H.sub.2 /1/2 Hr. C.E./ Prod. Hr Hg Prod. Hr After (ft.sup.3) % ppm (ft.sup.3) % ______________________________________ 1 Hr 0.12 91.4 -- 0.15 90.3 2 hrs 0.26 81.0 9.2 0.29 72.5 2.5 hrs 0.34 -- 27.0 0.40 -- 3 hrs 0.41 68.4 88.0 0.50 61.6 3.5 hrs 0.48 -- 257.4 0.43 -- 4 hrs 0.56 44.3 -- 0.16 57.5 5 hrs -- -- 0.14 97.3 ______________________________________ .sup.(a) Analysis of catholyte after Run 599522 by atomic absorption (AA) indicated 7.9 parts per billion of Hg and 12.2 parts per million of Pb indicating Hg had plated out on the Pb cathode.
TABLE IX ______________________________________ Electrochemical Reduction of TA to pHMBA With Mercuric Acetate Hg Run No. Run Hrs. Added pHMBA (5995) Each Day C.D. ppm F.C. g/hr % C.E. ______________________________________ 51-7/11 4.5 54 385 0.098 123 74 51-18 5.0 54 332 0.148 123 73 63 5.0 54 173 0.179 111 66 66 6.0 54 76 0.108 148 86 66 5.5 54 243 0.174 145 87 68 5.5 68 294 0.116 176 84 70 4.5 81 155 0.112 196 84 73 5.5 88 303 0.144 203 79 74 6.0 88 305 0.152 -- -- 78 7.0 88 603 0.164 211 82 79 6.5 88 454 0.189 214 79 85 7.0 88 452 0.193 219 81 86 7.0 88 454 0.193 212 78 110* 13.5 75 733 0.180 148 72 Total Hrs** 88.5 ______________________________________ Notes: C.D. = Current Density A/dm.sup.2 at end of each run F.C. = Final Concentration of pHMBA in g/ml C.E. = Current Efficiency *Used (NH.sub.4).sub. 2 CO.sub.3. All others used (NH.sub.4).sub.2 SO.sub.4. Same cell was used in all runs with no current reversals or shorting. **Total accumulative hours on same cathode without cleaning and/or amalgamation with a mercury bath.
Claims (23)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US06/319,120 US4381229A (en) | 1980-10-27 | 1981-11-09 | Process for electrochemical reduction of terephthalic acid |
CA000391991A CA1169017A (en) | 1981-11-09 | 1981-12-10 | Process for electrochemical reduction of terephthalic acid |
AU78785/81A AU548059B2 (en) | 1980-10-27 | 1981-12-22 | Process for making p-hydroxymethylbenzoic acid |
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US20113980A | 1980-10-27 | 1980-10-27 | |
US06/319,120 US4381229A (en) | 1980-10-27 | 1981-11-09 | Process for electrochemical reduction of terephthalic acid |
AU78785/81A AU548059B2 (en) | 1980-10-27 | 1981-12-22 | Process for making p-hydroxymethylbenzoic acid |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4431797A (en) * | 1982-11-30 | 1984-02-14 | Standard Oil Company (Indiana) | Preparation of poly(p-methylenebenzoate) copolyesters |
US4457814A (en) * | 1983-07-29 | 1984-07-03 | Standard Oil Company (Indiana) | Process for electrochemical reduction of terephthalic acid |
US4684449A (en) * | 1985-11-26 | 1987-08-04 | Mitsui Toatsu Chemicals, Inc. | Process for producing m-hydroxybenzyl alcohol |
EP1222953B1 (en) * | 1996-04-08 | 2010-05-05 | E.I. Du Pont De Nemours And Company | Process for the preparation of p-hydroxybenzoic acid |
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US3929613A (en) * | 1972-12-01 | 1975-12-30 | Rhone Poulenc Sa | Preparation of glyoxylic acid |
DE2510920A1 (en) * | 1975-03-13 | 1976-09-30 | Basf Ag | Electrochemical prepn of phthalide - from phthalic acid or anhydride, with final acidificn at controlled temp |
US3984294A (en) * | 1974-08-28 | 1976-10-05 | Basf Aktiengesellschaft | Electrochemical manufacture of pinacol |
DE2642496A1 (en) * | 1976-09-22 | 1978-03-23 | Basf Ag | PROCESS FOR THE PREPARATION OF P-HYDROXYMETHYLBENZOIC ACID |
-
1981
- 1981-11-09 US US06/319,120 patent/US4381229A/en not_active Expired - Fee Related
- 1981-12-22 AU AU78785/81A patent/AU548059B2/en not_active Ceased
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3929613A (en) * | 1972-12-01 | 1975-12-30 | Rhone Poulenc Sa | Preparation of glyoxylic acid |
US3984294A (en) * | 1974-08-28 | 1976-10-05 | Basf Aktiengesellschaft | Electrochemical manufacture of pinacol |
DE2510920A1 (en) * | 1975-03-13 | 1976-09-30 | Basf Ag | Electrochemical prepn of phthalide - from phthalic acid or anhydride, with final acidificn at controlled temp |
DE2642496A1 (en) * | 1976-09-22 | 1978-03-23 | Basf Ag | PROCESS FOR THE PREPARATION OF P-HYDROXYMETHYLBENZOIC ACID |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4431797A (en) * | 1982-11-30 | 1984-02-14 | Standard Oil Company (Indiana) | Preparation of poly(p-methylenebenzoate) copolyesters |
US4457814A (en) * | 1983-07-29 | 1984-07-03 | Standard Oil Company (Indiana) | Process for electrochemical reduction of terephthalic acid |
US4684449A (en) * | 1985-11-26 | 1987-08-04 | Mitsui Toatsu Chemicals, Inc. | Process for producing m-hydroxybenzyl alcohol |
EP1222953B1 (en) * | 1996-04-08 | 2010-05-05 | E.I. Du Pont De Nemours And Company | Process for the preparation of p-hydroxybenzoic acid |
Also Published As
Publication number | Publication date |
---|---|
AU548059B2 (en) | 1985-11-21 |
AU7878581A (en) | 1983-06-30 |
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